Plotting k^2 in Mathematica - Output Not 1?

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Discussion Overview

The discussion revolves around the output of a Mathematica plot involving Jacobi elliptic functions, specifically examining the expression involving \( k^2 \) and whether it yields a constant value of 1 across a specified range of \( t \). Participants explore the behavior of the functions and their expected properties based on mathematical theorems.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions the output of a Mathematica plot involving \( k^2 \) and Jacobi elliptic functions, expecting a constant value of 1 but observing a sinusoidal output instead.
  • Another participant confirms that the output oscillates between 1 and 2 in Mathematica version 12.0.0.0.
  • A participant references the addition theorems of Jacobi elliptic functions, suggesting that \( k^2 \text{sn}^2 + \text{dn}^2 = 1 \) should hold, raising the question of whether there is a misunderstanding.
  • One participant provides an alternative plot that appears to yield a constant value of 1 for all \( t \), while another expression does not, indicating variability based on the coefficients used.
  • There is a suggestion that the parameter used in JacobiSN and JacobiDN should be \( m \) instead of \( k \), noting that \( k = \sqrt{m} \), which may clarify the observed outputs.

Areas of Agreement / Disagreement

Participants express differing views on the expected output of the plots, with some confirming oscillation and others suggesting constant values under different conditions. The discussion remains unresolved regarding the implications of the addition theorems and the correct parameters to use.

Contextual Notes

There is a potential misunderstanding regarding the parameters \( k \) and \( m \) in the Jacobi functions, which may affect the interpretation of the results. The discussion also highlights the dependence on specific versions of Mathematica, which could influence the output.

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Can anyone confirm if the following in Mathematica gives an output that is not 1? I'm getting some sort of sinusoid, but I should get 1.

Code:
k = 2;
Plot[k^2 JacobiSN[t, k]^2 + JacobiDN[t, k]^2, {t, 0, 10}]

Thanks!
 
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joshmccraney said:
Can anyone confirm if the following in Mathematica gives an output that is not 1? I'm getting some sort of sinusoid, but I should get 1.

Code:
k = 2;
Plot[k^2 JacobiSN[t, k]^2 + JacobiDN[t, k]^2, {t, 0, 10}]

Thanks!
Yes, that oscillates between 1 and 2 (Mathematica 12.0.0.0).
 
I don't know if this helps, but

Code:
Plot[2 JacobiSN[t, k]^2 + JacobiDN[t, k]^2, {t, 0, 10}]

does appear to be 1 for all values of t while 4 JacobiSN[t, k]^2 + JacobiDN[t, k]^2 is not.

I noticed that by plotting the two functions separately and guessing the needed scale factor.
 
Bill Simpson said:
I don't know if this helps, but

Code:
Plot[2 JacobiSN[t, k]^2 + JacobiDN[t, k]^2, {t, 0, 10}]

does appear to be 1 for all values of t while 4 JacobiSN[t, k]^2 + JacobiDN[t, k]^2 is not.

I noticed that by plotting the two functions separately and guessing the needed scale factor.
Do you mean ##k^2## instead of 4?
 

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